fix: make character selection use characterIDs and not indices

src/main/java/uulm/teamname/marvelous/gamelibrary/config/CharacterConfig.java

@@ -22,6 +22,7 @@ public class CharacterConfig {
 
     @JsonIgnore private Map<String, CharacterProperties> propertyMap;
     @JsonIgnore private Map<String, CharacterProperties> unmodifiablePropertyMap;
+    @JsonIgnore private Map<Integer, CharacterProperties> idToCharacter;
 
     /**
      * @return a unmodifiable {@link Map}<{@link String}, {@link CharacterProperties}> containing all properties.
@@ -41,6 +42,23 @@ public class CharacterConfig {
         return unmodifiablePropertyMap;
     }
 
+    /**
+     * @return a {@link Map}<{@link Integer}, {@link CharacterProperties}> from characterID to character.
+     * If not yet existent, initialize the Map
+     */
+    @JsonIgnore
+    public Map<Integer, CharacterProperties> getIDMap() {
+        // lazy initialization
+        if (idToCharacter == null) {
+            idToCharacter = new HashMap<>();
+            for (CharacterProperties property: characters) {
+                idToCharacter.put(property.characterID, property);
+            }
+        }
+
+        return idToCharacter;
+    }
+
     @JsonIgnore
     public Tuple<CharacterProperties[], CharacterProperties[]> getDisjointSetsOfPropertiesOfSize(int size) {
         if ((size * 2) > characters.length) {